In manufacturing an electronic device, a silicon-containing film is etched by plasma. The silicon-containing film is made of a silicon-containing material such as silicon oxide or silicon nitride. For example, in manufacturing a NAND type flash memory having a three-dimensional structure, as the silicon-containing film, a multilayer film including a plurality of silicon oxide films and a plurality of silicon nitride films, which are alternately stacked on one another, is etched. A mask, which contains carbon such as amorphous carbon, is used as a mask to etch the silicon-containing film. An opening is formed in the mask.
The silicon-containing film needs to be etched in a film thickness direction thereof when the silicon-containing film is etched. That is, high verticality is required to etch the silicon-containing film. U.S. Patent Publication No. 2016/0343580 discloses a technology which protects a side wall surface that defines an opening formed by etching in order to obtain high verticality. Specifically, in one technology disclosed in U.S. Patent Publication No. 2016/0343580, a silicon-containing film is etched by plasma from fluorocarbon gas. In this technology, the side wall surface is protected by a carbon-containing material produced from fluorocarbon gas, and the silicon-containing film is etched by active species of fluorine produced from the fluorocarbon gas. In addition, in another technology disclosed in U.S. Patent Publication No. 2016/0343580, the process of etching the silicon-containing film by the active species of fluorine produced from the fluorocarbon gas and the process of forming a protective film by film forming processing are alternately performed.